1. Field of the Invention
This invention relates generally to field emission displays, and, more particularly, to a method for manufacturing a field emission display.
2. Description of the Related Art
Flat panel displays have recently been developed for visually displaying information generated by computers and other electronic devices. These displays can be made lighter and require less power than conventional cathode ray tube (CRT) displays. One type of flat panel display is known as a cold cathode field emission display (FED).
A field emission display uses electron emissions to illuminate a luminescent display screen and generate a visual image. An individual field emission pixel typically includes a face plate, having the display screen formed thereon, and emitter sites formed on a base plate. The base plate includes circuitry and devices that control electron emission from the emitter sites. For example, a gate electrode structure, or grid, is associated with the emitter sites. When a voltage differential is established between the emitter sites and the grid, electron emission is initiated. The emitted electrons pass through an evacuated space and strike phosphors contained on the display screen. The phosphors are excited to a higher energy level and release photons to form an image. In this system, the display screen is the anode and the emitter sites are the cathode.
The emitter sites and face plate are spaced apart by a small distance to stand off the voltage differential and to provide a gap for gas flow. To achieve reliable display operation during electron emission, a vacuum on the order of 10−6 Torr or less is required. The vacuum is formed in a sealed space contained within the FED.
Traditionally, FEDs are constructed as a package having a seal for sealing the evacuated space between the base plate and face plate. Typically, some type of a tube must also be provided for evacuating this space (“tubulating”) during construction of the FED package. The tube provides a conduit for pumping gases out of the sealed space during the evacuation of the sealed space, forming a vacuum. After the evacuation, the tube must also be sealed by pinching or by affixing a sealing member such as a plug.
One of the major problems delaying commercialization of FEDs is the lifetime problem associated with tip degradation. When electrons from tips of the emitter sites impinge on the phosphor anode display screen, certain materials are outgassed from the phosphor anode display screen. These outgassed materials then react with the tips of the emitter sites and reduce the emitted current.
A series of experiments have been run in a vacuum chamber to identify the materials outgassed from phosphor anode display screens. In particular, residual gas analyzers connected to the vacuum chamber for monitoring the materials outgassed from the phosphor anode display screens have been used. The results of the experiments indicate that carbon-based materials, including carbon dioxide (CO2) and carbon monoxide (CO), are the main materials outgassed from the phosphor anode display screens. The carbon-based materials come from both the wet chemical bath, where the anode screens are processed, and the ambient. The carbon-based materials are adsorbed and/or absorbed on the tips of the emitter sites and result in a higher work function φ and, consequently, a lower emission current over time, degrading and reducing the effective lifetime of the emitter tips and the associated FEDs.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.